C70 adsorbed on Cu(111): metallic character and molecular orientation

We investigated the interaction of C-70 with the Cu(111) surface using x-ray photoelectron spectroscopy and x-ray absorption spectroscopy. The data point to a net charge transfer from the Cu substrate to the C-70 molecules directly bonded to the Cu atoms, providing a metallic character for a single layer of C-70 (monolayer) adsorbed on this surface. A strong dependence of the x-ray absorption spectra from the light polarization is also observed. By comparing these experimental data with density-functional calculations of the contribution to the x-ray absorption spectral line shape of the five inequivalent carbon atoms in the C-70 cage, we observed that the molecules are mainly oriented with the C5V axis perpendicular to the Cu surface.